Improvement in the manufacture of paper-stock



UNITED STATES PATENT OFFICE.

MORRIS L. KEEN, OF JERSEY CITY, NEW JERSEY, ASSIGNOR TO HIMSELF ANDSAMUEL A. WALSH, OF NEW YORK CITY.

IMPROVEMENT IN THE MANUFACTURE OF PAPER-STOCK.

Specification forming part of Letters Patent No. 108.487, dated October18, 1870.

To all whom it may concern:

Be it known that I, MoRRIs L. KEEN, of Jersey City, in the State of NewJersey, have invented certain improvements in means or method of makin gpaper-pul p from wood straw, and analogous vegetable substances, and inthe treatment of the materials used therein, of which the following is adescription I will describe the invention as applied to the manufactureof pulp from poplar or analogous soft woods.

After wood has been reduced to line chips by any suitable cutter ormachine, the chips or shavings are put in a close strong boiler,

one of an upright form preferred, fitted with a with the interior of theboiler, so that the stock of pulp, when finished, can be discharged orblown out under pressure into a suitable receiver or tank for saidpurpose. The boiler is also provided with a top screen or perforateddiaphragm, fitted across the inside of the top of the boiler, allowing asteam-space above the Screen.

The boiler is charged either through a man hole above or below thescreen, a portion of the screen being removed in the former case toadmit of charge. After the boiler is charged with the wood and theman-hole secured, steam is admitted to boiler from a separate generator,by means of pipes at the top of the boiler, and manipulated at pleasure.After steaming the stock for thirty minutes (more or less, according tothe fineness of the shavings or chips) at a temperature of from 300 to400 Fahrenheit, the drain-cock is opened at the bottom and the condensedwater drawn off. Hot water is now injected, at a temperature of from 300to 400 Fahrenheit, above the screen into the steam-space, and percolatesfreely through the stock under treatment, and washes out theinterstitial matter.

By alternating the treatment from steam to water and water to steamevery five or ten minutes for thirty minutes or more, according to theprevious condition and kind of stock under treatment, it will be foundthat at least forty to fifty per cent. of the interstitial matter ofstraw or dry wood will have been removed and fifty to sixty per cent. ofgreen wood will have been removed.

All dry stock may be steeped with advantage in hot or cold water as apreliminaryprocess.

The charge is now ready for the alkaline treatment 5 but, if thoughtdesirable, it can be drawn from the boiler and more thoroughly washed,and more of the interstitial matter thus removed, or it can, in thisstage, he made into common brown paper.

The stock, as left in the boiler after the steam and hot-waterpercolation, may be transferred, with or without extra washing, toanother boiler, or retained in or returned to the same in which it wasoriginally steamed, and subjected to the action of alkali, either in acarbonate or caustic form, in solutions of the strengths andtemperatures described below, and, as most of the interstitial matterhas been previously removed, it is easily reduced to a pulp with aboutthirty-three per cent. of the alkali now used by any other of thepresent ap proved manufacture of wood or straw paperthatis to say, agood pulp can be produced by boiling the stock of wood or straw, &c.,previously cleaned of 1n uch of the interstitial matter by the steamingand hot-water process, in solutions of caustic alkali of twenty totwentyfive per cent. of wood pulp produced, and in eight or ten percent. of caustic alkali to straw pulp produced.

The strength of alkali preferred for wood is about 10 to 12 Baum; thatfor straw 6 to 8, though much weaker solutions will answer nearly aswell.

The alkali is first charged for wood at the rate of one gallon at 8 Baumto every pound of wood under treatment, and for straw one gallon at 5Baum to every pound of straw under treatment, and the heat raised in theboiler to a temperature indicated by ten to thirty pounds pressure onthe steam-gage.

I have made good pulp at ten pounds pressure, and have also pulpedthewood, straw, and similar materialsyhaving been previously acted on, inthe manner described, by steam and hot water in open vessels without anypressure whatever. It is, however, preferred to treat the stock, underthe pressure of thirty pounds, in a close boiler in caustic alkali ofstrength described, as the action desired is obtained under the heatindicated by that pressure in a shorter time than at a lowertemperature. With most stock this should be continued about one hour. Ido not, however, confine myself to the pressures or temperatures named,as higher pressure can be used to nearly equal advantage, and lowersteaming will answer the purpose; but those named seem to be about thebest for commercial use.

It is important that no considerable quantity of steam be allowed tocondense in the boiler at this stage, as it would weaken the strength ofthe solution. I therefore prefer to maintain the temperature by theadmission of steam, at a proper pressure, to an exterior jacket alone,or to a jacket and coils, or other provisions for heating the interior.

The construction of the boiler should, in this respect, depend much onits size. If the boiler is large, ample provision should be made forintroducing heating-surfaces, in its interior.

' If small, the heat may be maintained from the exterior sufficiently.

The alkali is now drawn off at the draincock in the bottom of theboiler, measure for measure-that is, the stock is now freed bypercolation and a sudden injection of steam in the top of the boilerover the stock.

The stock is now steamed again under high pressure, indicated by fromseventy to two hundred pounds by steam-gage, and hot water also injectedat the temperatures corresponding to those pressures, to which treatmentand which temperature the charge is kept fifteen or twenty minutes, andthen drawn out or blown out into a proper receiving-tank, drained andwashed by percolation, and assumes the condition of good gray pulp,ready for bleaching by any of the ordinary known methods.

The stock in a cleansed state, at this stage of process, prior to itsdischarge from the boiler, may be again subjected to percolation bysteam and hot water, so as to remove a great part of the extraneousmatter liberated by the last steaming and hot-water treatment, andasolution of weak chloride of soda, less than 1 Baum, admitted to theboiler, which is raised to a temperature of 300 for ten or fifteenminutes, and the stock then blown out. This greatly improves the colorof the stock.

The alkali drained off from the boiler is reserved and replenished forfuture use-that is, one-sixth of its original quantity is discarded andset aside for the recovery-furnace, and that quantity, by measure, at astrength of from 10 to 12 Baum for wood, and of the straw-liquor thesame quztntity-one-sixth-is discarded, and a fresh charge or amount ofonesixth new liquor or caustic alkali is added at a strength of 6 to 8Banm, or such strength as'to maintain the proper strength in the liquor;and this order is preserved of discarding one-sixth of alkali used inevery boiling and replacing the same with new alkali.

The waste or discarded alkali can be recov; ered in suitableevaporating-furnaces at a loss of from ten to fifteen per cent. forrecovery of said waste.

The boiler, in the alkaline treatment, may be heated by an auxiliarycoil, through which the large amount of alkali freely circulates, and inwhich the bulk is retained during the discharge of waste alkali, or anyother desirable method to economize time and heat.

The first steaming and hot-water treatment may be dispensed with, andgood pulp produced from straw and very finely -reduced woods ofnon-resinous character by simply boiling the same in solutions ofcaustic alkali of strength indicated, with the subsequent percolationsand steaming; but the renewal of liquor at subsequent boilings must, insuch case, be increased from two to three fold, as the interstitialmatter not removed by first steam and hot-water process has to beovercome by extra amount of caustic alkali.

Although I esteem the above process entire, and all the several novelparts thereof, more particularly valuable in its application to wood andstraw, I believe it may be used with much benefit on various other, and,in short, nearly or quite all, paper material. The first portion of ittowit, the extraction of most of the interstitial matter by the alternatesteam and hot-water treatment at high temperaturesI propose particularlyto employ in preparing paper-stock from hemp, fiax, and tow of either orboth. V

I can use carbonate of soda or other alkaline carbonates instead ofcaustic alkalies.

I claim as my invention in the pulping of wood and analogousmaterials- 1. The process of treating the material by a succession ofstages, pure steam and water and steam at a high temperature beingemployed at one stage and caustic alkali at a lower temperature atanother stage.

2. The percolation of steam downward through the mass ofpartially-treated fiber, so as to hasten the removal of the chemical, asspecified.

3. The triple treatment, first, with pure steam and water and steam atabout two hundred pounds pressure per square inch second, with causticalkali at twenty or thirty pounds per square inch; and, third, withsteam or water again at or near its previous high pressure, the severaloperations being com-' bined and made to succeed each other in themanner and for the purposes herein set forth.

4. The process of treating wood and analogons material for making pulpby steam and water alternately, substantially in the manner described,and for the purpose set forth.

5. The process of treating the stock by high steam and hot water priorto discharging the same out of the boiler, so as to aid in perfectlycleaning the fibers of all coloring matter.

6. The caustic alkali in weak solutions, in the proportions of twenty totwenty-five per cent. for wood pulp produced and eight to ten per cent.of straw pulp produced, either at low or high temperatures, when used inconnection with steam and hot-water process.

7. The process of treating wood or straw or analogous material incaustic alkali under pressure as named, as a first process, andsubsequent treatment of the stock by steam and hot Water, as described.

8. The process of treating wood or straw, &c., by steam and hot Water ata high temperature, as described, then the process of treating the stockin open vessels in caustic alkali,

as described, and the subsequent process of

